There could be a lot of reasons for it. . .maybe mutts and purebreds with improper conformation are more likely to be speutered earlier than purebreds with excellent conformation, and their poor conformation leads to the knee problems rather than the speutering, etc.
I mean, my cousin has blown ACLs in both knees and I assure you has plenty of testosterone, LOL. But he is heavy. So, yeah, i'd like to see a study done that takes all those things into account.
Correlation does not indeed equal causation. You really have to dig at studies to see what the methodology was, etc.
Slightly more than 50% of all dogs in the US are overweight. Every extra ounce means more pressure on the knees, and that pressure isn't ounce per ounce, it's multiplied by the force with which the paw hits the ground. So I'm not terribly surprised that lots of dogs have ACL injuries. How that relates to neutering, well, I'd have to know who neuters, at what age and why and how that relates to feeding choices. Most dog owners aren't intentional. They buy food they saw on TV that looks good. They walk their dogs somewhat regularly, train sit a few times and don't really think too much about the choices they make for their dogs. That type of owner, not at all negligent, but simply not overly involved, probably does speuter young because it's easy and it's heavily encouraged by the HSUS and ASPCA.
I know I'm rambling, but it's like saying poor people tend to be overweight in America because they don't eat well. That's true on the face of it, but there's a lot more to it than that.
